Not the styling. Our $43,400 tester, its curving profile the unbroken line of Infiniti’s "brush stroke” motif, looked at first glance the model of civility. Its Asgard Grey paint was the dark hue of a banker’s suit. Even its 14-spoke alloy rims seemed understated.

Yet this is not a car that will disappear in the crowd. Its tight curves and go-forward stance hint at power, even impatience. The careful detailing of its trim conveys a message of sophistication and achievement. The signals are subtle, but they are there.

The cabin? Fully in keeping with the exterior. Curve upon curve. Aerated leather, in the graphite black of our test car or a “Stone” grey we might select to brighten the space. Just enough brightwork. Gauges that glow, and well-placed dials and switches that spin and click smoothly.

It’s not huge, but it has a right-sized feel, especially from the obliging front sport seats with thigh-support extensions. The rear seat is of typical size for this class, maybe bigger than some, and the back doors swing open 80 degrees for better access.

Also typical is the fixed rear seatback to reduce road noise and body flex, with pass-through to the not-so-big trunk. Folding seats are for family cars.

The G25 is a new entry, of sorts, in this time-tested segment. It’s a styling ringer for Infiniti’s G37 but has a smaller engine, a new-to-North America 2.5-litre V-6.

It also becomes the least costly lineup member from Nissan’s luxury division, with a ground-floor price a notch below $34,000 (counting an advertised $2,500 “factory reduction”) for the base rear-wheel drive model. That car’s equipment mix, however, could send most buyers up a flight or two. High-intensity headlamps, pushbutton "Intelligent Key" ignition and seven-speed automatic transmission with sport mode come standard, but expected items such as dual-zone climate control, sunroof, even an auto-on-off function for the headlamps, are available only in a $4,900 "Touring" package. An all-wheel-drive version starts at $37,950 with a few more standard features.

Output from its small V-6 is 218 horsepower, unchanged from other G25s. That means the Sport is quick enough, especially in a sweet spot in the r.p.m. range that coincides with freeway entrance ramps. Desire a broader sweet zone, and Infiniti will oblige. Its larger 3.7-litre six-cylinder is rated at 328 h.p. in the G37 sedan ($40,950 to start) and 330 h.p. in a coupe model styled with a yet finer brush stroke.

Gear changes in our tester were a bit lazy, even when requested via paddles or floor shift. Perhaps the transmission’s driver-adaptive learning algorithm didn’t have time to catch our beat. More likely, the measured responses are part of the all-things-in-modulation nature of the G25.

Same with the suspension, which is firm enough to put some fun in cornering, but not so harsh as to let Ottawa’s bumpy roads spoil the morning commute. Pressed hard, the Sport tends to run wide in corners, a habit of many AWD cars. That and the weight penalty of all-wheel-drive had us wondering about the system’s value in a low-riding sedan that will hang up in deep snow, tire grip or not. But after a cross-town run through a spring rainstorm, all four tires adhering to the wet pavement, we were more sold on its benefits.

So what would we change in the G25? The satellite radio controls. Granted, no carmaker has found a easy way for drivers to sort through umpteen channels, store favourite stations and determine what song and artist they’re listening too. But the Infiniti’s theme-group system was especially hard to navigate.

And the exhaust note. Bit loud at times. Out of keeping with the overall, er, tone.

That these small items could represent the extent of our concerns is proof of the refinement Infiniti has brought to the G25 sport, and of the lasting appeal of the premium midsize sedan.